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Epigenetic regulation of transcription and virulence in Trypanosoma cruzi by O-linked thymine glucosylation of DNA

ABSTRACT: Unlike other eukaryotes, the protein coding genes of Trypanosoma cruzi are arranged into large polycistronic gene clusters transcribed by polymerase II (Pol II). Thus, trypanosomes rely on post-transcriptional processes to regulate gene expression. Here, we show that the glucosylated thymine DNA base (-D-glucosyl hydroxymethyluracil or base J) is present within sequences flanking the polycistronic units (PTU) in T. cruzi. loss of base J at sites of transcription initiation, via deletion of the two enzymes that regulate J synthesis (JBP1 and JBP2), correlates with an increased rate of Pol II transcription and subsequent genome-wide increase in gene expression. genes include virulence genes and the resulting parasites are defective in host cell invasion and egress. These studies indicate that base J represents an epigenetic factor regulating Pol II transcription initiation in kinetoplastids, and provides the first biological role of the only hyper-modified DNA base in eukaryotes. This entry contains the results using SLT, digital gene expression profiling of tags read off the spliced leader sequence of all mature trypanosomatid messages, for the life-cycle of T. cruzi, four stages, in wild-type as well as JBP1 KO cells.

ORGANISM(S): Trypanosoma cruzi

PROVIDER: GSE26754 | GEO | 2011/01/21

SECONDARY ACCESSION(S): PRJNA136343

REPOSITORIES: GEO

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Epigenetic regulation of transcription and virulence of Trypanosoma cruzi

Project description:Trypanosoma cruzi, a flagellated protozoan, is the causative agent of Chagas’ disease, a chronic and potentially fatal disease that causes irreversible damage to heart and digestive tract in humans. Like all trypanosomes, the protein coding genes of T. cruzi are arranged into large polycistronic gene clusters transcribed by polymerase II (Pol II). Therefore, trypanosomes presumably rely on post-transcriptional process to regulate gene expression. Pol II promoters have not been identified and there is no evidence for regulated gene expression at the transcriptional level. However, the presence of the hyper-modified DNA base J, Beta-D-glucosyl hydroxymethyluracil, at regions flanking the polycistronic units (PTU) in T. brucei suggested its involvement in regulating Pol II transcription. We now demonstrate that base J is localized at PTU flanking regions in T. cruzi and levels are differentially regulated by the thymidine hydroxylases, JBP1 and JBP2, involved in J biosynthesis. Microarray analysis of the JBP1dKO and JBP2dKO indicate the up and down regulation of several hundred genes distributed throughout the genome. We show a large increase in Pol II transcription rate following the decrease in base J at the PTU flanks. Changes in gene expression include virulence genes and parasites are defective in host cell invasion and egress. There is a direct correlation between the reduction in base J levels, number of genes affected and strength of the virulence phenotype. These studies indicate that base J represents an epigenetic factor regulating Pol II transcription initiation in kinetoplastids and provides a biological role of the only hyper-modified DNA base in eukaryotes. J1 and J2 null mutant trypomastigotes were each compared to wild type trypomastigotes. There were 3 biological replicates for each comparison.

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Project description:Base J, β-D-glucosyl-hydroxymethyluracil, is an epigenetic modification of thymine in the nuclear DNA of flagellated protozoa of the order Kinetoplastida. J is enriched at sites involved in RNA Polymerase (RNAP) II initiation and termination. We have previously demonstrated a role of J in regulating RNAP II initiation in Trypanosoma cruzi. Reduction of J in Leishmania tarentolae via growth in BrdU resulted in cell death and indicated a role of J in the regulation of RNAP II termination. To further explore J function in RNAP II termination among kinetoplastids and avoid indirect effects associated with BrdU toxicity and genetic deletions, we inhibited J synthesis in L. major and T. brucei using DMOG. Reduction of J in L. major resulted in genome-wide defects in transcription termination and the generation of antisense RNAs, without cell death. In contrast, loss of J in T. brucei did not lead to genome-wide termination defects; however, the loss of J at specific sites within polycistronic gene clusters led to altered transcription elongation and increased expression of downstream genes. Thus, J regulation of transcription termination genome-wide is restricted to Leishmania spp., while in T. brucei it regulates RNAP II elongation and gene expression at specific genomic loci. We studied the effect of loss of base J on transcription using WT and WT cells grown in DMOG-containing medium. We used 2 RNA-seq libraries containing processed RNA products and 4 small RNA libraries representing the entire transcriptome.

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Glucosylated hydroxymethyluracil (DNA base J) prevents transcriptional read-through in Leishmania

Project description:Some T's in nuclear DNA of trypanosomes and Leishmania are hydroxylated and glucosylated to yield base J (β-D-glucosyl-hydroxymethyluracil). In Leishmania about 99% of J is located in telomeric repeats. We show here that most of the remaining J is located at chromosome-internal RNA Polymerase II termination sites. Both this internal J and telomeric J can be reduced by a knockout of J-binding protein 2 (JBP2), an enzyme involved in the first step of J biosynthesis. J levels are further reduced by growing Leishmania JBP2 knockout cells in BrdU-containing medium, resulting in cell death. The loss of internal J is accompanied by massive read-through at RNA Polymerase II termination sites. The degree of read-through varies between transcription units, but may extend over 100 kb. We conclude that J is required for proper transcription termination and infer that the absence of internal J kills Leishmania by massive read-through of transcriptional stops.

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RNA polymerase II activity revealed by GRO-seq and pNET-seq in Arabidopsis

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